I’m very happy with my 5DII, but while that camera will seem to have superb low light/high ISO performance to anyone (like me) coming from any crop-sensor DSLR or lesser camera I’ve been interested by the superior low light performance of its successors. A few weeks ago I rented a 5DIII, and was impressed by that, and last weekend I rented a 6D and D600 to see how they compared. I had no intention of switching to Nikon, but I thought it might be fun to add a Nikon; the D600 was temptingly priced at the time, and a few Nikon lenses sound tempting (including the useful-sounding 28-300). So, I wanted to like the Nikon, dust/oil issues notwithstanding. But even if the D600 deals were still on, I wouldn’t want one because for my purposes there’s nothing about it that I prefer to the 6D or 5DIII. (My purposes are evidently rather more limited than those of many here: I’m not a professional photographer, I don’t shoot sports/action, and I have no interest in video. So there will be huge gaps in the comments that follow.)
I didn’t perform any serious reviewer-style tests involving studio/lab conditions, charts, etc. Rather, I wanted to see how they performed in conditions in which I actually use a camera, so I wandered around outside and inside, in low light and daylight, sometimes taking photos of the same things from the same place with each camera, at others just casually taking photos, always without a tripod. One day was spent with my other half, who hasn’t been into photography since the film era, knows little about digital cameras (nothing about these two) and is thus somewhat of a neutral observer; we switched cameras from time to time. I borrowed my father’s Nikon 50mm 1.8D and 85mm 1.8D, rented the Nikon 28-300 and used my own Canon 50mm 1.4, 85mm 1.8 and 70-300mm L. Everything was shot RAW + JPEG and viewed on a very good 30” monitor. Here are some observations, in no particular order (for all I know, of course, they only pertain to the precise bodies I rented).
1. Some have sneered at the fact that while the D600’s viewfinder is 100%, the 6D’s is only 97% (or whatever it is). What they don’t say is that the 6D’s is brighter and more accurate than the D600’s; the darker, slightly green hue on the Nikon’s makes everything look a bit drab, while what you see through the 6D has no coloration at all and is brighter. I didn’t notice this difference until the other half started complaining loudly about it, wondering at one point why anyone would even want to photograph what they saw through this viewfinder in the first place. He took a surprisingly strong dislike to the Nikon which didn’t change in the course of the day (I kept defending it, but not its viewfinder…).
2. I saw no evidence (on photos) of dust/oil on the D600’s sensor in “normal” photos (by which I mean that I didn’t deliberately take the sort of photo that would reveal them – no photos of the sky at f/16, for instance, though the sky appears in plenty of the photos I did take). That may be because (1) Lensrentals clean the sensor before sending it out and I didn’t take enough photos to reintroduce dirt (2) the camera I rented never had the problem in the first place (3) the camera had been used enough for the problem to have stopped of its own accord (4) dust doesn’t reveal itself in the sort of photos I take (in which case I don’t care about the problem) or (5) some other reason.
3. The D600 focused almost, but not quite, as well as the 6D in very low light. It struggled a couple of times, but that’s all, and for all I know that was as much the fault of the lens as the camera. Oddly, the only time it gave me a serious problem was outdoors in the middle of a cloudy day when there was enough light for the 85mm lens at 5.6 to trigger ISO 100: it completely failed to focus on a portion of a dark bronze statue. The Canon focused on the same portion of the statue as fast as always.
4. The greenish tint that others have noticed on the screen and which I’ve noticed through the viewfinder even ends up in RAW images, though it’s much subtler there. It may in part explain why Canon’s images look warmer (in varying degrees) than Nikon’s when processed via Lightroom using the same settings (it makes some colours look a bit muddy). Neither looks quite accurate, but I prefer Canon’s colours.
5. The D600 consistently exposed brighter (sometimes to an annoying degree) than the 6D except in one particular lighting scenario at night where the reverse was true. (My 5DII never does this.) Of course, it’s easy enough to change exposure (on Canons, at least… See below).
6. Assuming it’s true that the D600 has superior dynamic range, as we’re constantly being told, this didn’t reveal itself in any comparisons I made among the photos I took. In one dark photo, just for the heck of it, I brightened shadows as much as I could in lightroom, but the only difference I noticed was that there was a bit more noise in the Canon image than the Nikon equivalent – which I would have expected as it was darker in the first place. (I seldom lighten shadows at all, and when I do it’s not by much, and the 6D’s images responded just fine.)
7. I generally prefer the photos taken with the Canon to those taken with the Nikon, but there’s not much in it. Processed RAW files from both cameras are very impressive and the differences would likely strike most people as trivial (on smaller monitors they may be even less noticeable); I suspect that in a line-up most couldn’t tell which were taken with which camera. Most differences could likely be removed via further tweaking with software.
8. The 6D’s images in very low light/high ISO do indeed have a bit less noise than the D600.
9. But even if the images looked exactly the same, I still wouldn’t want a D600 because I don’t like how the controls work (not the menus; they seem easy enough to figure out); my first DSLR was a Nikon D3100 and I was instantly reminded of one reason why I disliked using it: both make changing even some of the most basic setting so awkward it’s as though they’re trying to force you to stay in fully-automatic mode. When I moved from Pentax to the 5DII I was able to figure just about everything out without looking at the manual; but it took me a rather long and frustrating time, including rereading the instructions more than once, to figure out something as elementary as setting the D600 to use center point focusing. Why does making so many changes require simultaneously holding down one button with one hand while turning a wheel with the other? Presumably one could get used to all this, and if the Nikon took better pictures than the Canon it would be worth the effort; but it doesn’t (at least, not for my purposes).
10. Finally, I’m obviously not in a position to make sweeping pronouncements about Canon lenses vs Nikon lenses. All I will note is that the photos I took with the Canon 85 1.8 are sharper (especially wide open) than those taken with the Nikon and have less chromatic aberration, that the two 50mm lenses are closer in daylight (I think the Canon is a bit sharper, but by a trivial degree), that the Nikon 50mm creates shocking amounts of coma at night (only a tiny area in the center seems free from it), that the two Canon primes seem mechanically a bit better than the two Nikons (for all I know their –G successors are better), and that the superiority of the 70-300L (both mechanically and in terms of image quality) to the Nikon 28-300 far exceeds the difference in price (and while 28-300 seems like a desirable range, it should be noted that much of the time it’s nowhere near 300, thanks to a rather excessive degree of focus breathing.)
That’s already more than enough, so I’ll stop!